Biology subjects

Strzalka, A.

Publications and source records attributed to Strzalka, A..

7 recordsLinked to original sources

bioRxiv2024

Significance of the CTP-binding motif for the interactions of S. coelicolor ParB with DNA, chromosome segregation and sporogenic hyphal growth.

The segregation of bacterial chromosomes is widely mediated by partitioning proteins (ParAB). While ParB binds DNA specifically by recognising short, palindromic sequences known as parS sites, ParA utilises its ATPase activity to generate the force to translocate ParB-DNA nucleoprotein complexes (segrosomes). The assembly of the segrosome requires the association of ParB with parS, followed by nonspecific spread of the protein along the DNA. To spread on DNA, the ParB dimer must entrap the parS site within the complex, a process triggered by CTP binding to the conserved GERR amino acid motif. In Streptomyces, a genus of soil-dwelling, multigenomic bacteria that have a complex life cycle, ParB-dependent chromosome partitioning is initiated during the growth of sporogenic hyphae. However, the molecular mechanisms underlying segrosome formation in Streptomyces and their ability to coordinate with sporogenic development remain incompletely understood. In this study, we advance the understanding of chromosome segregation in bacteria by exploring the effects of CTP binding and hydrolysis on the formation of the partitioning complex in S. coelicolor. Here, via in vitro approaches, we demonstrate that a conserved GERR motif is essential for CTP binding and hydrolysis by S. coelicolor ParB. Moreover, the motif is crucial for CTP-dependent ParB accumulation on DNA. Using mutant strains, we show the significance of the GERR motif for segrosome complex assembly. Additionally, we provide data showing that the CTP-binding motif contributes to the regulation of the growth of sporogenic cells. Overall, we show that CTP-dependent segrosome assembly impacts the development of S. coelicolor sporogenic cells.

molecular biology↗

bioRxiv2024

SMC modulates ParB engagement in segregation complexes in Streptomyces

ParB is long established chromosome segregation protein in bacteria. Due to the recently demonstrated CTPase activity of ParB, formation of its nucleoprotein complexes was unrevealed. ParB homodimers bound to CTP are loaded onto DNA at parS sites, where they recruit condensin (SMC), thereby facilitating chromosome organization and segregation. Whether SMC modulates ParB complexes has remained unknown. Here, we generated Streptomyces venezuelae strains producing ParB-HaloTag in the presence or absence of SMC and used single-cell time-lapse fluorescence microscopy, single molecule tracking and fluorescence recovery after photobleaching analysis to explore ParB dynamics. Additionally, we performed chromatin immunoprecipitation to examine ParB interactions with DNA in the presence or absence of SMC. We reveal that SMC modulates ParB complex stability on DNA. We find that the absence of SMC results in faster ParB complex disassembly, and promotes non-specific DNA binding. Additionally, we show that SMC reduces ParB CTPase activity in vitro. Taken together our data provide evidence of SMC positive feedback on the ParB nucleoprotein complex, offering new insight into the nature of ParB complex regulation.

microbiology↗

bioRxiv2024

CemR atypical response regulator impacts energy conversion in Campylobacteria

Campylobacter jejuni and Arcobacter butzleri are microaerobic food-borne human gastrointestinal pathogens that mainly cause diarrheal disease. These related species of the Campylobacteria class face variable atmospheric environments during infection and transmission, ranging from nearly anaerobic to aerobic conditions. Consequently, their lifestyles require that both pathogens need to adjust their metabolism and respiration to the changing oxygen concentrations of the colonization sites. Our studies revealed that C. jejuni and A. butzleri lacking a Campylobacteria-specific regulatory protein, C. jejuni Cj1608 or a homologue A. butzleri Abu0127, are unable to reprogram tricarboxylic acid cycle or respiration pathways, respectively, to produce ATP efficiently and, in consequence, adjust growth to changing oxygen supply. We propose that these Campylobacterial energy and metabolism regulators (CemR) are long-sought transcription factors controlling the metabolic shift related to oxygen availability, essential for these bacterias survival and adaptation to the niches they inhabit.

molecular biology↗

bioRxiv2023

Profiling of the Helicobacter pylori redox switch HP1021 regulon using a multi-omics approach

The gastric human pathogen Helicobacter pylori has developed mechanisms to combat stress factors, including reactive oxygen species (ROS), which are present in the stomachs harsh environment. Here, we present a comprehensive study on the redox switch protein HP1021 regulon combining transcriptomic, proteomic and DNA-protein interactions analyses. Our results indicated that HP1021 decides about H. pylori response to oxidative stress. HP1021 regulon included 498 genes, of which 411 responded to oxidative stress. HP1021 controlled typical ROS response pathways (katA, rocF) and less canonical ones, particularly DNA uptake and central carbohydrate metabolism. We identified HP1021 as the first molecular regulator of competence in H. pylori, as HP1021-dependent repression of the comB DNA uptake genes was relieved under oxidative conditions, increasing natural competence. Furthermore, HP1021 controlled glucose consumption by directly regulating the gluP transporter and had an important impact on maintaining the energetic balance in the cell.

molecular biology↗

bioRxiv2023

The interplay between the polar growth determinant DivIVA, the segregation protein ParA and their novel interaction partner PapM controls the Mycobacterium smegmatis cell cycle by modulation of DivIVA subcellular distribution

Bacterial chromosome segregation is facilitated by the ParABS system. The ParB protein binds centromere-like parS sequences and forms nucleoprotein complexes. These nucleoprotein complexes are segregated by the dynamic ATPase ParA. In mycobacteria, ParA also interacts with the polar growth determinant DivIVA (Wag31). This interaction was earlier shown to facilitate the segregation of ParB complexes but also to affect cell extension. Here, we identify an additional partner of ParA in Mycobacterium smegmatis, named PapM. Using E. coli based analysis, we show that PapM likewise interacts with DivIVA and that the tripartite interaction of ParA-PapM-DivIVA is phosphorylation-dependent: ParA binding to DivIVA is diminished, while PapM binding is promoted upon phosphorylation of DivIVA. The presence of PapM enhances the dissociation of ParA from the DivIVA complex upon its phosphorylation. Studies of M. smegmatis mutant strains reveal that altered PapM levels influence chromosome segregation and cell length. The elimination of PapM affects ParA dynamics. Further, ParA and, to a lesser extent, PapM modulates the subcellular distribution of DivIVA. Altogether our studies show that the tripartite interplay between ParA-DivIVA and PapM controls the switch between cell division and cell elongation and in this way affects the mycobacterial cell cycle. ImportanceThe genus of Mycobacteria includes important clinical pathogens (M. tuberculosis). Bacteria of this genus share the unusual features of their cell cycle such as asymmetric polar cell elongation and long generation time. Markedly, control of the mycobacterial cell cycle still remains not fully understood. The main cell growth determinant in Mycobacteria is an essential protein DivIVA, which is also involved in cell division. DivIVA activity is controlled by phosphorylation but the mechanism and significance of this process is unknown. Here, we show how the previously established protein interaction partner of DivIVA in Mycobacteria, the segregation protein ParA, affects the DivIVA subcellular distribution. We also demonstrate the role of a newly identified M. smegmatis DivIVA and ParA interaction partner, a protein named PapM, and we establish how their interactions are modulated by phosphorylation. Demonstrating that the tripartite interplay affects the mycobacterial cell cycle contributes to general understanding of mycobacterial growth regulation.

microbiology↗

bioRxiv2022

Binary or non-binary fission? Reproductive mode of a predatory bacterium depends on prey size

Most eukaryotic and bacterial cells divide by binary fission, where one mother cell produces two progeny cells, or, rarely, by non-binary fission. All bacteria studied to date use only one of these two reproduction modes. Here, we demonstrate for the first time that the predatory bacterium Bdellovibrio bacteriovorus reproduces through both binary and non-binary fission. Switching between the two modes correlates with the prey size. In relatively small host cells, B. bacteriovorus undergoes binary fission; the FtsZ ring assembles in the midcell and the mother cell splits into two daughter cells. In larger host cells, B. bacteriovorus switches to non-binary fission and creates multiple FtsZ rings to produce three or more daughter cells. Completion of bacterial cell cycle critically depends on precise spatiotemporal coordination of chromosome replication and segregation with other cell-cycle events, including cell division. Our studies reveal that B. bacteriovorus always initiates chromosome replication at the invasive pole of the cell, but the spatiotemporal choreography of subsequent steps depends on the fission mode and/or the number of progeny cells. In non-binary dividing filaments producing five or more progeny cells, the last round(s) of replication may also be initiated at the noninvasive pole. Finally, we show that binary-dividing B. bacteriovorus needs to extensively rebuild the flagellated pole of the mother cell to turn it into the invasive pole of a daughter cell. Altogether, we find that B. bacteriovorus reproduces through bimodal fission and that extracellular factors, such as the host size, can shape replication choreography, providing new insights about bacterial life cycles.

molecular biology↗

bioRxiv2020

Spatial rearrangement of the Streptomyces venezuelae linear chromosome during sporogenic development

Depending on the species, bacteria organize their chromosomes with either spatially separated or closely juxtaposed replichores. However, in contrast to eukaryotes, significant changes in bacterial chromosome conformation during the cell cycle have not been demonstrated to date. Streptomyces are unique among bacteria due to their linear chromosomes and complex life cycle. These bacteria develop multigenomic hyphae that differentiate into chains of unigenomic exospores. Only during sporulation-associated cell division, chromosomes are segregated and compacted. In this study, we show that at entry to sporulation, arms of S. venezuelae chromosomes are spatially separated, but they are closely aligned within the core region during sporogenic cell division. Arm juxtaposition is imposed by the segregation protein ParB and condensin SMC. Moreover, we disclose that the chromosomal terminal regions are organized into domains by the Streptomyces-specific protein - HupS. Thus, we demonstrate chromosomal rearrangement from open to close conformation during Streptomyces life cycle.

microbiology↗